The LairClear Sky ChartHistory

This sumarizes the distribution of each different forecast outcome for the The Lair clear sky chart from 2005-11-05 to 2017-09-22.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as
clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because
good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to
interpret. The observing conditions section counts the combinations of conditions needed for common types of
astronomical observation.

Percentages are of nighttime hours per month, or per year, when a particular observing
conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.